Hacky sacks are sacks full of sand, saw dust and gravel, or mass produced filler used in commercial made sacks. One way to hacky sack is to count how many times you can kick the sack before it hits the ground and see which player can kick it the most times, or players can make a circle and pass the hacky sack around. Hacky sacks are popular with young people and are often carried in a pocket to take out and play whenever there is some free time.
Another game played by people is called "Two Hit Thunder". The object of this game is to hit the sack twice to yourself and then kick it at another player. It doesn't count if you don't hit it twice, although hitting it more is acceptable. Each time a player is hit they get a strike. Three strikes and you're out of the game. At any time a player can block the incoming sack with the bottom of their foot provided they don't go in the other players area. If you are hit by the sack, you can cancel out the hit by saving it with a stall (where you "catch" the sack with the top of your foot, pinning it between your knees, etc.) or by keeping the sack in play by kicking it..